Jig for grinding turbine blades of jet engines



A. BRENNING July 18, 1967 JIG FOR GRINDING TURBINE BLADES OF JET ENGINES 2 Sheets-Sheet Filed Nov. 27. 1964 ul EHIMH' INVENTOR.

NNING ALBERT BRE 8Y2 ATTORNEY July 18, 1967 A. BRENNING 3,331,166

JIG FOR GRINDING TURBINE BLADES OF JET ENGINES Filed Nov. 27, 1964 2 Sheets-Sheet 2 INVENTOR.

ALBERT BRENNI WWJ W ATTORNFY ill/0 I HHI H IHIH lllll" United States Patent 3,331,166 JIG FOR GRINDING TURBINE BLADES 0F JET ENGINES Albert Brenning, P.O. Box 167, San Mateo, Calif. 94401 Filed Nov. 27, 1964, Ser. No. 414,250 8 Claims. (Cl. 51-217) ABSTRACT 01 THE DISCLOSURE A jig for supporting a turbine blade of a jet engine, the blade having a spoke that is concavo-convex in cross-section and provided with a shroud at its outer end. When the blade is supported in the jig with the convex side of the spoke disposed uppermost, one edge of the shroud may be ground parallel with an average air foil plane by reciprocating a grinding wheel back and forth across the shroud. Upon turning the blade upside down to present the concave side of the spoke uppermost and supporting the blade in the jig, the opposite edge of the shroud may be ground at a predetermined airfoil angle relative to the average airfoil plane as the grinding wheel is reciprocated across the shroud.

The present invention relates to improvements in a jig for grinding turbine blades of jet engines. It consists of the combinations, constructions, and arrangement of parts, as hereinafter described and claimed.

In the jet engine art, it is common practice to provide a series of turbine blades, each blade having a tapered fluted inner section that is adapted to be secured in a correspondingly-shaped recess in a rotor. Also, the outer end of each blade is provided with a shroud, and the shrouds of adjacent blades interfit with one another to form a complete circle around the rotor.

It is necessary from time to time to remove the turbine blades and restore their interfitting edges of the shrouds by welding and grinding. This has presented a complex problem in the industry that is time consuming, since the blades must have their shrouds restored with accuracy so that the blades need not be discarded, especially due to untrue grinding.

Moreover, each blade has a concavo-convex spoke, and the edge of the shroud on the convex side of the spoke must be ground parallel with an average airfoil plane of the blade, while the opposite edge of the shroud on the concave side of the blade must be ground at a predetermined airfoil angle relative to this plane.

The cardinal object of this invention is to provide a jig that will support a turbine blade of a jet engine so that the proper grinding may be readily accomplished, when a grinding wheel is reciprocated back and forth across the shroud with a rim of the wheel moving in a rectilineal path. When the edge of the shroud is being ground on the convex side of the spoke, the blade is supported in one position by the jig, while the blade is turned upside down and supported in another position when the shroud is being ground on the concave side of the spoke. In either event, the blade is clamped in the proper position, and the clamping rneans is easily operated to hold the blade in position on the jig and conveniently released by a simple operation.

In actual tests of the jig, it has been found that many times more blades may be restored in a given shift than when using jigs heretofore provided.

Other objects and advantages will appear as the specification proceeds, and the novel features of the invention will be set forth in the appended claims.

3,331,156 Patented July 18, 1967 Drawings For a better understanding of the invention, reference should be had to the accompanying drawings, forming part of this specification, in which:

FIGURE 1 is a side elevational view of my jig for grinding turbine blades of a jet engine;

FIGURE 2 is an isometric view of one of the turbine blades that is to be ground;

FIGURE 3 is a longitudinal vertical section view taken along the plane 33 of FIGURE 2, and showing the shroud at the outer end of the turbine blade;

FIGURE 4 is a top plan view of my jig;

FIGURE 5 is a transverse vertical section view taken along the plane 5-5 of FIGURE 1, and disclosing a front rest for the shroud end of the turbine blade;

FIGURE 5A is a fragmentary view similar to FIG- URE 5, but showing a modified form of a front rest; and

FIGURE 6 is a vertical transverse sectional view taken along the plane 66 of FIGURE 1, and illustrating a rear rest for the shroud end of the turbine blade.

While I have shown only the preferred forms of my invention, it should be understood that various changes, or modifications, may be made within the scope of the appended claims, without departing from the spirit of the invention.

Detailed description In order that functioning of my jig may be readily understood, the structural features of one of the turbine blades A will first be set forth. The blade has a spoke B that is concave-convex in transverse section, the blade being provided with a shroud C at its outer end, the shroud having opposing edges 10 and 11 to be ground, the edge 10 being arranged on the concave side 12 of the spoke B and the edge 11 being disposed on the convex side 13 of this spoke. The blade A is further provided with an inner end section 14 having flutes 15 formed on the concave and convex sides of the spoke.

It will be noted that the inner end section 14 tapers, and it is adapted to be inserted into a corresponding shaped recess in a rotor D, as suggested by the dot-dash lines in FIGURE 2 of the drawings. The tapered fluted inner end 14 is commonly referred to in the art as a fir tree.

Referring now to FIGURE 3, it should be noted that when the edge 11 on the convex side 13 of the spoke is ground, it will be parallel with an average airfoil plane E, the extended line 16 indicating the grind on the edge 11. This average airfoil plane is further shown in FIG- URES 1 and 5 of the drawings. However, when the edge 10 on the concave side 12 of the spoke is ground, it will make a predetermined airfoil angle a relative to the average airfoil plane E (see FIGURE 3).

Now I shall describe the details of my jig the turbine blades A. In FIGURES 1 and 4, a supporting block F has been shown, and this block is secured to a base 17. This block supports front and rear wedgeshaped splines 18 and 19, respectively, the wedge portions of these splines projecting above the supporting block F, as shown in FIGURE 1. It will be seen that the front spline is mounted at a lower elevation on the supporting block than the rear spline.

As shown in FIGURES l, 4 and 5, a front rest G is provided to support the outer shroud end of the blade A, when the convex side 13 of the blade is disposed uppermost and the front spline 18 is inserted between adjacent flutes 15 on the inner end section 14 of the blade on the concave side 12 of the spoke B. The blade will be supported at this time for grinding the edge 11 of the shroud C parallel with the average airfoil plane E when for grinding a grinding wheel H is reciprocated back and forth across the shroud with a rim 20 of the wheel moving in a rectilineal path 16a that coincides with the extended line 16 (see FIGURES 1 and 3).

The front rest G is provided with a notch 21 of the shape shown in FIGURE 5 for receiving and supporting the shroud C when the convex side 13 of the spoke B is disposed uppermost, as disclosed by full lines in FIGURE 1. The notch 21 is further illustrated in FIGURES 1 and 4 of the drawing. This rest is adjustably secured to the base 17 by bolts 22 that pass through slots 23 formed in the lower parts of the rest (see FIGURE 5). Thus the front rest G may be adjusted laterally in a transverse direction relative to the base 17. As a modified form of a front rest, I show a post G in FIGURE 5A that has its lower end 24 threaded into the base 17, and a nut 25 secures this post in adjusted position. The upper tip 26 of this post is adapted to bear against the concave side 12 of the spoke B, when the edge 11 of the shroud C is being ground.

Turning to FIGURES 1, 4 and 6 of the drawings, a rear rest I has been provided to support the outer shroud end C of the blade A, when the latter is turned upside down to present the concave side 12 of the spoke B uppermost and the rear spline 19 is inserted between adjacent flutes 16 on the inner end section 14 of the blade on the convex side 13 of the spoke. The blade is supported at this time for grinding the opposite edge of the shroud C at the predetermined airfoil angle a relative to the average airfoil plane E when the grinding wheel H is moved across the shroud with its rim moving in the rectilineal path 16a.

The rear rest I is provided with a bar 27 disposed to engage with the shroud C, with this bar being adjustable vertically relative to the base 17. For this purpose, the bar 27 fits into a guideway 28 of a bracket 29, and an adjusting screw 30 is provided for raising and lowering the bar 27 with respect to the bracket 29 (see FIGURE 1). The upper end 31 is wedge-shaped, as shown in FIG- URE 6, so as to fit the edge 11 of the shroud C. The adjusting screw 30 is further shown in FIGURE 6 of the drawings.

In order to hold the inner end section 14 of the blade A in engagement with the front and rear splines 18 and 19, respectively, I provide toggle clamps K and K, respectively. Both of these toggle clamps are identical with one another, and are shown in FIGURES 1 and 4. The same reference numerals will be applied to corresponding parts of these toggle clamps.

Each toggle clamp is provided with a clamping arm 32 that has an adjustable stud 33 at its outer end designed to bear against the inner end section of the blade A, as shown in FIGURE 1. Moreover, each clamping arm 32 has its inner end swingably secured by a journal pin 34 to a bracket 35, the latter being fixed by screws 36 to the supporting block F. Each toggle clamp has an operating lever 37 that is swingably attached by a journal pin 38 to its associated clamping arm 32, and a link 39 has its ends attached by journal pins 40 and 41 to the levers 37 and brackets 35, respectively.

It will be noted that the clamping levers 37 and the clamping arms 32 are movable into raised positions, as shown by the toggle clamp K in FIGURE 1, for releasing the blade A. As clearly disclosed in FIGURE 4, the clamping arms 32 are arranged on opposite sides of a medial vertical longitudinal plane 42 of the jig, when they are raised, whereby either clamping arm 32 may be lowered into clamping position without interference by the other clamping arm. These clamping arms extend angularly relative to the longitudinal plane 42, with the clamping ends of these arms substantially coinciding with the plane 42 when lowered.

Thus the clamping toggles K and K may be operated with facility and ease when it is desired to clamp the turbine blade in position for a grinding operation.

As to the grinding wheel H, it is made of the electrolytic type, with one wire 43 of an electrical circuit being connected to the wheel (see FIGURE 1). Another wire 44 of the electrical circuit may be connected to the base 17. Electrolyte is applied to the rim 20 of the grinding wheel H by an applicator L, the latter being secured to the base 17 by bolts 45 and having a notch 46 through which the marginal rim portion of the wheel is reciprocated. Electrolyte may be supplied through a fitting 47 to a passageway 48 that leads to the rim-receiving notch 46. This electrolyte establishes a path for flow of electricity from the wheel H, through the shroud C of the turbine blade A when the edge 10 or 11 is being ground, thence through the base 17 to the wire 44. Of course, the wires 43 and 44 are connected to a suitable source of electricity so that the edges 10 and 11 will be ground by being burned.

For the purpose of adjusting the rear rest I laterally, the base 17 is provided with a transverse guideway 49 in which the bottom of this rest is guided (see FIGURES 1 and 6). Bolts 50 pass through slots 51 formed in the lower base part 52 of the rest J and are threaded into the base 17.

In FIGURE 5, the front rest G has a notch 53 formed therein so that a micrometer may be used for measuring the distance from the edge 53 of this notch to the inclined part 54 of the edge 11 of the shroud C. Both edges 10 and 11 are zig-zag in outline.

The rectilineal movement of the grinding wheel H is indicated in FIGURE 1 by the double-ended arrow 55 in this view of the drawings.

I claim:

1. In a jig for grinding a turbine blade of a jet engine, in which the blade has a spoke that is concavo-convex in transverse cross-section, the blade being provided with a shroud at its outer end, the shroud having opposing edges on the concave and convex sides of the blade, and the blade further being provided with an inner end section having flutes formed on the concave and convex sides of the spoke, the combination of:

(a) a supporting block having front and rear wedgeshaped splines, the front spline being mounted at a lower elevation on the supporting block than the rear spline;

(b) a front rest disposed to support the outer end of the blade, when the convex side of the spoke is disposed uppermost and the front spline is inserted between adjacent fiutes on the inner end section of the blade on the concave side of the spoke, with the blade being supported at this time for grinding one edge of the shroud parallel with an average airfoil plane when a grinding wheel is reciprocated back and forth across the shroud with a rim of the wheel moving in a rectilineal path;

(c) and a rear rest disposed to support the outer end of the blade, when the latter is turned upside down to present the concave side of the spoke uppermost and the rear spline is inserted between adjacent flutes on the inner end section of the blade on the convex side of the spoke, with the blade being supported at this time for grinding the opposite edge of the shroud at a predetermined airfoil angle relative to said average airfoil plane when the grinding wheel is moved across the shroud in said path.

2. The jig for grinding a turbine blade of a jet engine,

as set forth in claim 1;

(d) and in which clamping means are provided for holding the inner end section of the blade in engagement with the front and rear splines, when the convex and concave sides, respectively, of the spoke are disposed uppermost.

3. The jig for grinding a turbine blade of a jet engine,

as set forth in claim 1;

(d) and in which a first toggle clamp is provided with a clamping arm engageable with the inner end of the blade for holding the flutes on the concave side of the spoke in engagement with the front spline;

(e) and a second toggle clamp provided with a clamping arm engageable with the inner end of the blade for holding the flutes on the convex side of the spoke in engagement with the rear spline.

4. The jig for grinding a turbine blade as set forth in claim 3;

(f) and in which each toggle clamp is provided with an operating lever, and the clamping arms are movable into raised positions for releasing the blade.

5. The jig for grinding a turbine blade of a jet engine,

as set forth in claim 4;

(g) and in which the clamping arms are arranged on opposite sides of a media-l vertical longitudinal plane of the jig when they are raised, whereby either clamping arm may be lowered into clamping position without interference by the other clamping arm;

(h) the clamping arms extending angularly relative to said longitudinal plane when these arms are lowered, with the clamping ends of the arms substantially coinciding with said longitudinal plane.

6. The jig for grinding a turbine blade as set forth in claim 1;

(d) and in which the front rest is provided with a notch disposed to receive and support the shroud of a jet engine,

of a jet engine,

when the convex side of the spoke is disposed uppermost. 7. The jig for grinding a turbine blade as set forth in claim 1; (d) and in which the front rest is provided by a post secured to a base. 8. The jig for grinding a turbine blade as set forth in claim 1;

(d) and in which the rear rest is provided by a bar of a jet engine,

of a jet engine,

10 disposed to engage with the shroud, with this bar being adjustable vertically relative to a base.

References Cited UNITED STATES PATENTS 2,577,747 12/1951 Gibian 29156.8 3,035,831 5/1962 Blatt 269201 FOREIGN PATENTS 493,775 2/1950 Belgium.

369,878 3/1932 Great Britain. 689,941 4/ 1953 Great Britain.

HAROLD D. WHITEHEAD, Primary Examiner. 

1. IN A JIG FOR GRINDING A TURBINE BLADE OF A JET ENGINE, IN WHICH THE BLADE HAS A SPOKE THAT IS CONCAVO-CONVEX IN TRANSVERSE CROSS-SECTION, THE BLADE BEING PROVIDED WITH A SHROUD AT ITS OUTER END, THE SHROUD HAVING OPPOSING EDGES ON THE CONCAVE AND CONVEX SIDES OF THE BLADE, AND THE BLADE FURTHER BEING PROVIDED WITH AN INNER END SECTION HAVING FLUTES FORMED ON THE CONCAVE AND CONVEX SIDES OF THE SPOKE, THE COMBINATION OF: (A) A SUPPORTING BLOCK HAVING FRONT AND REAR WEDGESHAPED SPLINES, THE FRONT SPLINE BEING MOUNTED AT A LOWER ELEVATION ON THE SUPPORTING BLOCK THAN THE REAR SPLINE; (B) A FRONT REST DISPOSED TO SUPPORT THE OUTER END OF THE BLADE, WHEN THE CONVEX SIDE OF THE SPOKE IS DISPOSED UPPERMOST AND THE FRONT SPLINE IS INSERTED BETWEEN ADJACENT FLUTES ON THE INNER END SECTION OF THE BLADE ON THE CONCAVE SIDE OF THE SPOKE, WITH THE BLADE BEING SUPPORTED AT THIS TIME FOR GRINDING ONE EDGE OF THE SHROUD PARALLEL WITH AN AVERAGE AIRFOIL PLANE WHEN A GRINDING WHEEL IS RECIPROCATED BACK AND FORTH ACROSS THE SHROUD WITH A RIM OF THE WHEEL MOVING IN A RECTILINEAL PATH; 